The purpose of the Mouse Biology and Stem Cell Core is to provide a wide range of murine-based assays for investigators from Project 1-3. Specific aims include (1) evaluation of normal mice and genetic (mutant) strains for LD50 (survival) after radiation, tissue pathology, hematopoietic cell culture, and chromose breakage (2) evaluation of IF profiles (signature profiles) (3) evaluation of biodosimetry in mice and (4) evaluation of candidate radioprotective agents in mice. Based on preclinical data in the mouse model, we will determine suitable radioprotective agents for further study.